With the reduction of the size of selective call receivers and the need for portableness and convenience, selective call receivers have primarily depended upon battery power supplied by limited energy content batteries. Thus, users desire power conserving methods in the selective call receivers for improving their battery life. One of the primary current draining circuits in a selective call receiver is the receiver circuitry. The receiver circuitry must be energized to allow the selective call receiver to receive radio frequency (RF) signals intended for reception by the selective call receiver, however, the receiver circuitry can be de-energized during other operations of the selective call receiver.
An example of a conventional power conserving method involves determining whether the carrier frequency indicates transmissions intended for the selective call receiver are being received. It can be quickly determined whether a carrier frequency is received, but a selective call receiver system may broadcast numerous types of information on the carrier frequency, some of which are not intended for the selective call receiver which may cause an unknowing receiver to expend battery power unnecessarily.
Also, selective call receivers can improve their battery life by having the receiver circuitry energized only during portions the signaling protocol to be received. Typically, battery saving methods require that the selective call receiver knows when addresses are transmitted within the signaling protocol. For example, conventional battery saving methods take advantage of frame assignments and the occurrences of addresses at predetermined positions within the signaling protocol, for example the Post Office Code Standardization Advisory Group (POCSAG) signaling protocol, by de-energizing the receiver circuitry during the portions of the signaling protocol when the address of the selective call receiver is not being transmitted. According to the POCSAG signaling protocol, before detection of its address, the selective call receiver detects preamble and the synchronization codeword which enables the selective call receiver to achieve synchronization to the paging transmission.
However, selective call receivers, when receiving paging transmissions, do not know the exact time when the current paging transmission will end and when the next transmission will begin. Therefore, because the selective call receiver is ignorant of the beginning and ending of each transmission, the receiver circuitry is energized for an unnecessarily long time to decode information until the selective call receiver has determined that the current transmission has ended and a new transmission has began.
Thus, what is needed is a battery saving method for increasing the period of time the receiver circuitry is de-energized by determining the beginnings and endings of paging transmissions being received.